1. Field of the Invention
The present invention relates in general to a car heater for warming the passenger room of a motor vehicle, and more particularly to a passenger room heating system which is incorporated with a so-called "boiling liquid engine cooling system".
2. Description of the Prior Art
A so-called "boiling liquid engine cooling system (viz., evaporative cooling system)" has been proposed for achieving cooling of an internal combustion engine. This type cooling system basically features an arrangement in which a liquid coolant (for example, water or a mixture of water and antifreeze or the like) in the coolant jacket of the engine is permitted to boil and the gaseous coolant thus produced is passed out to an air-cooled heat exchanger or radiator where the gaseous coolant is cooled and liquefied and then recirculated back into the coolant jacket of the engine. Due to the excellent heat exchange effected between the gaseous coolant in the radiator and the atmosphere surrounding the radiator, the cooling system exhibits a very high performance.
Apart from the above, various kinds of car heaters have been hitherto proposed and put into practical use. However, most of the car heaters hitherto proposed are of a type which is designed for use with a conventional "water cooled type engine cooling system" which uses water in liquid state for cooling the engine.